JPH02269784A - Steel plate coating composition - Google Patents

Abstract

PURPOSE:To prepare a steel plate coating compsn. excellent in the applicability, gloss, stain resistance, boiling water resistance, dispersibility, and hardness by compounding a polyester derived from a specific glycol and an alkyl- etherified formaldehyde resin. CONSTITUTION:A polyester derived from at least one glycol selected from the group consisting of 2-butyl-2-ethyl-1,3-propanediol and 2,2-diethyl-1,3- propanediol and an alkyl-etherified formaldehyde resin (e.g. methoxylated methylolurea, methoxylated methylolmelamine) are compounded to give a steel plate coating compsn. excellent in the applicability, gloss, stain resistance, boiling water resistance, dispersibility, and hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition for coated steel sheets that has excellent processability and is excellent in gloss, stain resistance, dispersibility, boiling water resistance, and hardness.

The first characteristic required of a painted steel sheet is that it has excellent workability such as press working. There are many paints currently in use, including alkyd resins, acrylic resins, vinyl resins, and silicone resin paints, but if the emphasis is placed on processability, all of them will inevitably have drawbacks in other properties, making them difficult to use. Currently, there are restrictions on

Solution-type vinyl resin is generally used in paints that have a high degree of processability.
There are vinyl chloride orgasol, plastisol, and vinylidene fluoride paints, but solution-type vinyl resin paints have poor stain resistance, solvent resistance, and boiling water resistance, while vinyl chloride orgasol paints and plastisol paints have poor gloss and stain resistance. , solvent resistance is extremely poor, and vinylidene fluoride paints have poor gloss and are expensive, so they are not versatile. On the other hand, when using alkyd resin or acrylic resin paints to obtain good workability, the paint film becomes considerably soft and lacks hardness.

On the other hand, when trying to obtain a coating film with high hardness, a coating film with sufficient workability cannot be obtained.

Commonly used alkyd resins contain dicarboxylic acids such as isophthalic acid, orthophthalic acid, and adipic acid as acid components, and glycols such as ethylene glycol, propylene glycol, and neopentyl glycol as alcohol components, as well as trimethylolpropane and pentaerythritol sodium. It is a polyester resin containing at least 10 mol % of the total alcohol component or the total acid component of a polyalcohol having a valence of 3 or more or a polycarboxylic acid having a valence of 3 or more such as trimellidic acid. However, when the hardness of materials containing isophthalic acid or orthophthalic acid exceeds a certain level, they lack flexibility and flexibility, resulting in the so-called hard coating surface and the ability to form a coating film with excellent workability. was difficult. Therefore, in order to improve the physical properties of the coating film, efforts have been made to obtain an improved coating film by using a relatively large amount of trivalent or higher-valent components and increasing the crosslinking density.

In addition, Japanese Patent Publications No. 34273/1982 and Japanese Patent Publication No. 21830/1987 discuss alcohols as raw materials for coating compositions for painted steel sheets.

However, conventional coating compositions for coated steel plates have insufficient dispersibility, boiling water resistance, processability, gloss, stain resistance, and hardness, and further improvements are desired.

Taking these current circumstances into consideration, the present inventors have developed a product that has excellent dispersibility, boiling water resistance, and processability, as well as stain resistance, solvent resistance, and adhesion, and has an extremely high level of gloss that has never been seen before. As a result of extensive research in order to obtain coated steel sheets, they discovered that the desired objective could be achieved by blending an alkyl etherified aminoformaldehyde resin with a specific polyester, and thus arrived at the present invention.

That is, the present invention provides 2-butyl-2-ethyl-1,3-
Propanediol (hereinafter abbreviated as DMH) and 2,2
-diethyl-1,3-propanediol (hereinafter referred to as DMP
This coating composition for painted steel sheets is made by blending an alkyl etherified formaldehyde resin with a polyester made of one or more glycols selected from the following.

In the present invention, DMH or DMP is preferably 45 mol% or more as a glycol component, and glycols other than DMH or DMP include ethylene glycol, propylene glycol, trimethylene glycol, 1.4-butanediol, 1.3-butanediol, Neopentyl glycol, 2-ethyl-1,3-hexanediol, 2
．． 2. There are alkylene glycols such as 4-trimethyl-1,3-pentanol. DMH Mata It
DMP imparts excellent adhesion, water resistance, and dispersibility to coating films, and this is presumed to be because DMH or DMP has a special structure. In the polyester of the present invention, alcohols with a valence of 341[i or more can be used, and examples of alcohols with a valence of 3 or more include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, etc. If it exceeds 10 mol%, the coating film tends to become hard and have low flexibility, so 10 mol% or less is preferable.

The dicarboxylic acid used in the polyester of the present invention is preferably an aromatic dicarboxylic acid, and in addition to isophthalic acid, examples include terephthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, 4゜4'-diphenyldicarboxylic acid, and the like. .

These aromatic dicarboxylic acids can be arbitrarily selected and used from the viewpoint of economical efficiency and physical properties of the coating film.
Particularly preferred is isophthalic acid or isophthalic acid and terephthalic acid from the viewpoint of corrosion resistance, weather resistance, and boiling water resistance.

Among the dicarboxylic acids, the amount of inphthalic acid is preferably 20 to 100 mol%, more preferably 40 to 85 mol%. If less than 20 mol % of isophthalic acid is added, the solubility in organic solvents will be insufficient, resulting in poor coating work. As the dicarboxylic acid component of the present invention, in addition to aromatic dicarboxylic acids, oxycarboxylic acids such as p-oxybenzoic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid can also be used.

Furthermore, trivalent or higher valence carboxylic acids can be used in an amount of 0 to 10 mol % based on the total acid components, and examples of trivalent or higher valence polycarboxylic acids include trimellidic acid and pyromellitic acid.

Trivalent or higher polycarboxylic acid is 10 mol% of the total acid component
If it exceeds this, the coating film tends to become hard and less flexible.

The alkyl etherified formaldehyde resin used in the present invention is formaldehyde that has been alkyl etherified with an alkyl alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, n-propatool, impropatool, n-butanol, isobutanol, or It is a condensation product of paraformaldehyde etc. and urea, N, N-ethylene urea, dicyandiamide, aminotriazine, etc., specifically methoxylated methylol urea, methoxylated methylol-N, N-monoethylene urea, methoxylated methylol Examples include dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine.

The coating composition of the present invention has a ratio of the polyester to the alkyl etherified formaldehyde resin of 95 to 70:5.
It is preferable that it is 30 (weight ratio).

If the proportion of the copolymerized polyester exceeds 95% by weight, the desired stain resistance and hardness will be insufficient, which is undesirable. Moreover, if it is less than 70% by weight, post-processability will be poor, which is not preferable.

The coating composition of the present invention may contain p-)cyansulfonic acid, phosphoric acid monoalkyl ester, and amine salt of p-)cyansulfonic acid as a curing catalyst. The amount of catalyst used is 0 to 5% by weight based on the formaldehyde resin.

Furthermore, the coating composition of the present invention is generally used in a form dissolved in an organic solvent. Examples of organic solvents include toluene, xylene, and Trupetz 100. 500,
Ethyl acetate, butyl acetate, methyl cellosolve, butyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, ethylene glycol monoacetate, butanol, octatool,
It can be arbitrarily selected from diacetone alcohol, carpitol acetate, methoxybutyl acetate, etc. depending on its solubility and evaporation rate.

In many cases, the coated steel sheets that are the object of the present invention are coated at high speed and baked at high temperatures for short periods of time.
It is desirable to use a mixture of two or three or more of the above solvents. Generally, it is desirable to use 90 to 30% by weight of aliphatic hydrocarbon or aromatic hydrocarbon and 10 to 70% by weight of polar solvent such as esters, ketones, and ethers.

The coating composition of the present invention exhibits sufficient performance even when applied and baked, but if further improvement in corrosion resistance is required, epoxy resin, such as a commercially available epoxy resin, may be used as a primer coating agent. Epicote 83
4. +001. 1004. 1009 (manufactured by Shell Chemical Co., Ltd.), Araldite Ei097 (manufactured by Ciba Geigy), polyester resins such as Vylon RV
-2!110 (manufactured by Toyobo Co., Ltd.) etc. are used.

The baking temperature of the coating composition of the present invention may be arbitrarily selected depending on the size and thickness of the steel plate, the baking capacity of the furnace, the hardenability of the coating material, etc.

Mixing machines such as roll kneaders, ball mills, blenders, etc. are used to manufacture coating compositions. For coating, roller coating, roll coater spray coating, electrostatic coating, etc. are selected as appropriate.

Additives such as pigments such as titanium oxide, glass fiber silica, and wax may be added to the coating composition of the present invention depending on the purpose and use.

The coating composition of the present invention has excellent workability after being applied to a steel plate, and the coated surface has excellent stain resistance, solvent resistance, and adhesion, and has unprecedented extremely high gloss and good dispersion. have sex.

〔Example〕

Examples are given below to explain the present invention more specifically, but the present invention is of course not limited to the same extent by the Examples. In addition, below, parts indicate parts by weight, and %
% indicates weight %.

Each measurement item was measured according to the following method.

(1) Reduced viscosity η sp/c (dl/g) 0.10 g of polyester was dissolved in 25 cc of a mixed solvent of phenol/tetrachloroethane (volume ratio 6/4) and measured at 30°C.

(2) Softening point Measured according to JIS K-2351.

(3) Hardness The painted surface of the steel plate was measured according to JIS K-s4oo using a high-grade pencil specified in JIS S-8008.

(4) Gloss eo'' reflectance was measured.

(5) DuPont impact value A DuPont impact tester was used, and the load was 1.0 kg.

(1/2)" was dropped onto the paint film from a predetermined height, and the maximum height without causing cracks on the paint surface was taken as the measured value (J I
SK54600).

(6) Flexibility The painted steel plate was bent 180 degrees and cracks at the bent portion were measured. ○ indicates no abnormality. × indicates cracks. 3T refers to the case where three sheets of the same thickness are sandwiched in the folded part.

(7) Apply stain-resistant oil-based ink to the painted surface 0.5 cm x 2 cm,
After being left for 24 hours at °C, the degree of staining was measured by wiping with methanol-impregnated gauze. O is good, Δ
is defective, × is insufficient.

(8) Pheasant Roll Resistance The coated surface was rubbed with Phizirol soaked in absorbent cotton, and the number of times the coated surface was rubbed until the bare surface was exposed. (9) Boiling Water Resistance The condition was determined after immersion in boiling water for 2 hours.

O means good, × means bad.

(10) Dispersibility Dispersibility is determined by the naked eye to determine whether the coating film has uniform color without color separation.

O is good, X is bad Examples 611 parts of dimethyl terephthalate, 748 parts of dimethyl isophthalate, 71 Ei parts of ethylene glycol, DM
Part He+e, 51.5 parts glycerin, 0.61 parts zinc acetate
A reaction vessel was charged with 0.61 parts of antimony trioxide and 0.61 parts of antimony trioxide, and a transesterification reaction was carried out from 140°C to 220°C over 4 hours while blowing NN2. then 40
The pressure was reduced to 30mm and 11g over a few minutes, and the temperature was further increased to 255°C2.
The polycondensation reaction was carried out at 0 to 25 mmHg for 60 minutes. Next, 13.5 parts of trimellidic anhydride was added and reacted at 255°C for 10 minutes to obtain polyester (A).

Polyesters (B) to (E) whose polyester compositions are shown in Table 1 were synthesized in the same manner.

Polyesters (A) to (E) were each treated with fluorohexanone/
It was dissolved in a mixed solvent of Tsurupetz-150 (weight ratio: 50,150), and the nonvolatile content was adjusted to 40%.

100 parts of the above polyester (A) solution, 40 parts of titanium oxide
Part, methyl etherified methylolmelamine (trade name:
10 parts of Sumimaru M-40S, nonvolatile 80%, produced by Sumitomo Chemical Industries, Ltd., 0.5 parts of p-toluenesulfonic acid solution (benzyl alcohol 20% solution), and 0.20 parts of Polyflow S (manufactured by Kyoeisha Yushi Chemical Industries) were ball milled. The mixture was kneaded for one day and a night to obtain a coating composition for coated steel plates.

Similarly, the coating compositions shown in Table 2 were prepared by replacing the polyester (A) with polyesters (B) to (E), or by replacing the alkyl etherified amine formaldehyde resin with methyl etherified methylol melamine or butyl etherified melamine resin. Obtained.

These paint compositions were applied to a galvanized iron plate (J
IS G-3302) was applied to a test piece treated with a zinc phosphate solution to a film thickness of 15 to 20μ, and then 2
Baking was performed at 10°C for 2 minutes.

The test results of the obtained coated steel plate are shown in Table 2.

It has been revealed that the coating composition for painted steel sheets according to the present invention has particularly good gloss, and when the glycol component is mainly DMH or DMP, it has excellent boiling water resistance and pigment dispersibility.

Table *) Comparative Polyester Table (*1) Super Beckamine J-820 (Dainippon Ink Chemical Industry Rip)

Claims (1)

[Claims] A coating made by blending an alkyl etherified formaldehyde resin with a polyester made of one or more glycols selected from 2-butyl-2-ethyl-1,3-propanediol and 2,2-diethyl-1,3-propanediol. Paint composition for steel plates.